This invention relates generally to optical interfaces for data communication and, more particularly, to optical interfaces with improved alignment capability.
Optical data communications technology has a number of advantages over wire technology, such as bandwidth, data rate and response characteristics superior to those of conventional wire technology. Also, optical technology is essentially immune to radio frequency interference (RFI) and electromagnetic interference (EMI) issues associated with wire technology. Optical data communication is therefore desirable in a variety of applications such as multi-chip modules (MCMs), printed circuit board (PCB) technologies, and integrated backplanes.
In conventional optical connectors, electronic circuitry, optical source and optical detectors are typically mounted on PCBs which are received in card guides mounted to an equipment frame. A backplane mounted to the rear of the frame includes board edge connectors aligned with the card guides and electrical conductors interconnecting the board edge connectors. The circuit boards are provided with board edge electrical contacts which are received in the board edge connectors when the circuit hoards are slidably inserted in the card guides to electrically connect the circuitry to the electrical conductors on the back plane. The electrical conductors provide the required electrical connections between circuit board.
The circuit boards also include optical connector parts which are optically coupled to the optical sources and to the optical detectors of the receivers and transmitters. The board mounted optical connector parts must be mated with frame mounted optical connector parts to optically connect the optical sources and the optical detectors to optical fibers terminating on the frame mounted optical connectors.
In the current board edge optical connector arrangements the circuit board mounted optical connector parts are mounted at leading edges of the circuit boards. These leading edges are already congested with board edge electrical contacts. In addition, in the board edge optical connector arrangements the frame mounted optical connector parts are mounted at the back plane which is already congested with electrical board edge connectors and electrical conductors. In current systems, optical fibers are left to hang loose between packs or bundles of fibers which tends to create a xe2x80x9crat""s nestxe2x80x9d of fibers.
In view of these problems it is a purpose of the present invention to provide an apparatus and method to connect large numbers of optical fibers to an optical backplane and avoid the xe2x80x9crats nestxe2x80x9d problem associated with multiple fiber-to-fiber connections and/or routing systems.
It is another purpose of the present invention to provide an improved optical interface between a mother board and a daughter card (or backplane) involving 90 degree turns and pluggable connections.
It is another purpose of the present invention to provide arrays of interconnects utilizing waveguides and fibers.
These and other purposes of the present invention will become more apparent after referring to the following description considered in conjunction with the accompanying drawings.
The purposes and advantages of the present invention have been achieved by providing an apparatus for forming a staircase arrangement for the connection of optical waveguides between a card and backplane comprising:
a card having first optical waveguides, the first optical waveguides having a low index of refraction region surrounding a high index of refraction core region;
electrical conductors embedded in the card, and where the card has a first edge ending in a staircase arrangement;
optical fiber-ribbons having a low index of refraction region surrounding a high index of refraction core region and having one end in close proximity with the first optical waveguides, the optical fiber-ribbons protruding from the first edge;
a first guidance structure connected to the first edge and the first guidance structure containing channels to guide and align the optical fiber-ribbons, and having a first inner side comprising a staircase arrangement and a first outer side having an inclination;
a backplane having second optical waveguides, the second optical waveguides having a low index of refraction region surrounding a high index of refraction core region;
additional electrical conductors embedded in the backplane, and the backplane having a second edge ending in a second staircase arrangement; and
a second guidance structure connected to the second edge, the second guidance structure having a second inner side comprising a staircase arrangement and a second outer side having an inclination and tapered openings which receive and guide a second end of the optical fiber-ribbons into close proximity with the second optical waveguides when the outer side of the first guidance structure is brought into contact with the outer side of the second guidance structure, thereby forming a staircase arrangement of connected waveguides between a card and backplane.
The fiber-ribbons may have a D-shaped cross section such that the high index of refraction core region is in close proximity to a flat edge of the D-shaped cross section and the flat edge is in close proximity to the first and second optical waveguides. This close proximity is necessary for efficient core to core coupling. The fiber-ribbons may be a multi-mode high refractive index polymer optical fibers with bend radii of approximately 1 mm.
The apparatus may also have grating structures formed in the low index of refraction region of the first or second optical waveguides or in the core regions of either the waveguide or fiber ribbon to enable grating-assisted coupling.
It is another object of the invention to provide a method for forming a connection of optical waveguides between a card and backplane comprising the steps of:
providing a card having first optical waveguides, said first optical waveguides having a low index of refraction region surrounding a high index of refraction core region;
forming a first edge in the card ending in a first staircase arrangement;
providing fiber-ribbons having a low index of refraction region surrounding a high index of refraction core region and having a first end in close proximity with the first optical waveguides, the fiber-ribbons protruding from the first edge;
connecting a first guidance structure to the first edge, the first guidance structure containing channels to guide and align the fiber-ribbons and having a first inner side comprising a staircase arrangement and a second outer side having an inclination;
providing a backplane having second optical waveguides, the second optical waveguides having a low index of refraction region surrounding a high index of refraction core region;
forming a second edge ending in a second staircase arrangement;
connecting a second guidance structure to the second edge, the second guidance structure having a second inner side comprising a staircase arrangement and a second outer side having an inclination and tapered openings;
inserting a second end of the fiber-ribbons into the tapered openings which receive and guide the second end of fiber-ribbons; and
placing the outer side of the first guidance structure into contact with the outer side of the second guidance structure thereby placing the fiber-ribbons into close proximity with the second optical waveguides and forming a staircase arrangement to connected waveguides between a card and backplane.